1. Field of the Invention
The present invention relates to a printed circuit board (PCB) and a method of manufacturing the PCB and more particularly, to a PCB having improved adhesion between a metal thin film and a resin material, and a method of manufacturing the PCB.
2. Description of the Related Art
Printed circuit boards (PCB) are essential in various electronic and machine equipments.
The PCB is formed by attaching a copper foil onto one side or both sides of a polymer insulating board formed of epoxy or polyimide, and circuits are formed on the copper foil by etching or plating.
Various attempts at improving adhesion between the copper foil and the polymer insulating board have been developed.
One method of improving adhesion includes strengthening adhesion between a polymer resin and the copper foil by coating the surface of the copper foil with a polar polymer. However, since such a method depends on chemical coupling, there is a limit to how much the adhesion is improved. In addition, in a cross-linking process performed on the polar polymers at a high temperature, internal pressure is generated as organic compounds evaporate, thereby forming defects, such as bubbles.
Another method involves physically or chemically forming nodules on the surface of the copper foil, thereby improving adhesion between the copper foil and the polymer resin through an uneven surface-structure of nodules. Widely used methods of forming nodules on the surface of the copper foil include jet scrubbing, brush grinding, and soft etching. However, in the soft etching, since the nodules have a thickness of about 1-2 μm, the circuit has a non-uniform width and etching linearity deteriorates. Also, after the nodules are formed, an oxide film is formed on the surface of the copper foil so that a process of removing the oxide film is needed.